Linear Sigma Model at finite baryonic density and symmetry breakings

Abstract

The linear sigma model at finite baryonic density with a massive vector field is investigated considering that all the bosonic fields develop non zero expected classical values, eventually associated to condensates and corresponding to dynamical symmetry breakings which might occur in the QCD phase diagram. A modified equation for the classical vector field is proposed with its respective solution. Some in medium properties of the model (mainly masses) are investigated within reasonable prescriptions. In particular the behavior of the {\it in medium} pion and sigma masses and a particular way of calculating {\it in medium} coupling to baryons is investigated. A symmetry radius for finite baryonic densities is proposed and calculated in different ways in terms of the other variables of the model and these different ways of calculating it agree quite well. However, assuming that the pion and sigma masses go to zero close to the restoration of chiral symmetry a too high value for the critical density is obtained $\rho_c \simeq 4.3 \rho_0$.